Theatregoing is often classified as relaxation. However, anyone attending some of this summer's shows should be ready to do some work. Privacy, James Graham's tremendous play at the Donmar about the consequences of new media and communication, asks its audience, in contradiction of regular theatrical protocol, not only to switch their mobiles on, but to use them – as directed by the actors.

Kevin Toolis's The Confessions of Gordon Brown, starting another run at the Ambassadors theatre in June, includes a more old-fashioned type of interactivity, as Ian Grieve, who uncannily embodies the former Labour prime minister in this enjoyable monologue, poses questions to the audience and sometimes has to answer them too.

These follow a number of recent productions – including One Man, Two Guvnors and Dame Edna Everage's Eat Pray Laugh – that invite volunteers from the audience to join the action on stage, a pantomime and standup comedy tradition that seems increasingly to have extended to straight theatre. The obvious disadvantage of civilians over members of Equity is the risk they become blush-struck and tongue-tied in public. The clear benefit is that they are happy to pay, rather than be paid, for the privilege of taking part.

And customer-actors are likely to become a more common sight. Whereas Privacy aims to bring to theatre an equivalent of digital connectivity, other examples of audience participation reflect a growing perception (shared with TV and radio) that, in an era of tweeting and texting, the entertainment media can no longer treat the audience merely as passive receivers.

Even in pre-digital theatre, some authors thought about making spectators part of the spectacle. In A Day in the Death of Joe Egg (1967), Peter Nichols asks the ticket buyers to portray a class of pupils being taught by his teacher protagonist, while in the same dramatist's A Piece of My Mind (1986), they perform various supporting roles, including a field of sheep.

Incorporating the audience into the performance risks making a paying public uncomfortable. The Holy Terror (1991) was one of Simon Gray's least successful plays, I suspect because the clientele tired of representing the members of a Women's Institute reading group being addressed by the central character. And the fact that Look, Look (1990) was a rare flop for Michael Frayn might have been due to similar reasons. Its cleverly self-reflective concept – in which theatregoers sat watching actors playing people who had gone to see a play – was possibly a better idea on the page than on the stage.

People who have paid money for an evening's entertainment (in London's West End, often a lot of money) can be uneasy about being made to feel self-conscious or uncomfortable about being there. The Austrian author Peter Handke has insisted that his 1966 "anti-play" Offending the Audience is actually a manifesto for better drama and, therefore, pro-audience. But it would be understandable if some potential ticket buyers struggled to get past the title. If we wanted accusation or abuse, we'd stay at home.

The intellectual point being made is clear enough: we should be doing more to protest present-day government-sponsored torture in Guantanamo Bay or Syria. But, as a theatregoer, it seemed unfair – had we tried to storm the boards and free Winston, we would we have been ejected by ushers – and itinterrupted my appreciation of an otherwise engrossing production.

Challenges to the audience contract are even more irritating when they occur in a poor show: as when, in Peter Shaffer's 1985 flop Yonadab, a character accused us of being "voyeurs" for mutely witnessing a staged rape. Peeping toms seek out certain things to see; viewers of new plays stumble on them unawares. Most of us would have been happy never to repeat the voyeurism, and the risk was, anyway, low – the play has not been revived.

The most common use of an audience, though, remains as sudden (and, generally, reluctant) participants in the action. Though popular, this tactic is problematic. Some comedians have complained that, in a time of sophistication about the media and cynicism about most things, audiences often assume participating members of the public to be stooges, even if they aren't.

The people hauled from the stalls by Dame Edna to take part in Eat Pray Laugh's game show were providing such fruitful feed lines to the antipodean diva that I became convinced they were part of the acting company, although, if they were, they meticulously maintained the impression of awestruck luck when they returned to seeming friends or relatives in the stalls. Humphries has made startling use of planted patsies in the past: the theatre director Michael Blakemore, in his memoir Stage Blood, describes as the greatest theatrical trick he ever witnessed was in an earlier Dame Edna show when a fan appeared to fall out of the upper circle while struggling to catch a chucked gladiolus.

The illusionist Derren Brown, who makes the kind of show that would be ruined by any suspicion of complicity, became so irritated by the knowing approach of his audience that, in his current tour Infamous , he chooses contributors by hurling a frisbee at apparent random into the auditorium.To dispel any further suspicion that Brown is targeting plants, the catcher is then asked to throw the thing unseeingly over his or her shoulder. This method also addresses a frequent complaint about audience participation: that the stalls are disproportionately favoured over the cheaper seats.

Having seen the show twice with no overlapping participants, I accept that Brown was picking strangers. However, other performers and productions are more loose with the truth and, on different occasions, I have experienced being taken in and suddenly rumbling what was going on.

The clues are often very subtle. If a performer physically touches or kisses a civilian participant, you can assume they are probably a stooge. No sane producer would risk the lawsuit or visit from Operation Yewtree that might result from fumbling with someone unknown in this way. In another interactive play, I was completely convinced the audience helper was real – so convincingly shy she could barely look at the actors – until the moment when a member of the cast handed her a glass of wine.

Again, the giveaway was the legal jeopardy: if randomly selected, the spectator might prove to be a recovering alcoholic or taking medication that excludes booze. Derren Brown often asks his volunteers about their medical history before consenting to experiment on them. Alternatively, as prop plonk is usually fruit juice, the interloper might blow the scene by commenting on the pretend beverage.

Now I think about it, perhaps the interacting audience members at The Confessions of Gordon Brown were actually actors. The rise of audience participation has introduced a new form of tension for audiences: are the "real people" really real?

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